Portable data collection devices are widely used in manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, etc. for inventory control, tracking, production control and expediting, quality assurance and other purposes. Various bar code dataform readers have been proposed for portable data collection devices including laser scanners and one dimensional (1D) charge coupled device (CCD) imaging assemblies, both of which are capable of reading 1D bar code dataforms, that is, bar codes consisting of a single row of contrasting black bars and white spaces of varying widths. Both of these readers are also capable of reading a "stacked" two dimensional (2D) bar code dataforms such as PDF417, which has row indicator patterns utilized by the reader for vertical synchronization.
A two dimensional (2D) imaging based dataform reader has been proposed in U.S. application Ser. No. 08/544,618, filed Oct. 18, 1995 and entitled "Extended Working Range Dataform Reader Including Fuzzy logic Image Control Circuitry". The 2D dataform reader disclosed in application Ser. No. 08/544,618, which is assigned to the assignee of the present application, includes an imaging assembly having a two dimensional array of photosensors (also referred throughout as photodiodes or pixels) adapted to read 2D bar code dataforms (e.g., PDF417, SuperCode, etc.) with vertical synchronization row indicator patterns as well as matrix dataforms (e.g., MaxiCode, DataMatrix, etc.) which do not include vertical synchronization patterns. The 2D dataform reader disclosed in application Ser. No. 08/544,618 utilizes an open loop feedback control system including fuzzy logic circuitry to determine proper exposure time and gain parameters for a camera assembly. Application Ser. No. 08/544,618 is incorporated in its entirety herein by reference.
In U.S. application Ser. No. 08/797,552, filed Jan. 31,1997 and entitled "Portable Data Collection Device with Crosshair Targeting Illumination Assembly," a portable data collection device was disclosed utilizing a two dimensional imaging assembly selectively actuatable for imaging and decoding a target bar code or matrix dataform and for capturing the image of a target image area. The device including a viewing assembly and a modular camera assembly with a targeting illumination assembly to assist in aiming the device at the target dataform to be decoded or the target area whose image was to be captured. U.S. application Ser. No. 08/797,552 is incorporated in its entirety herein by reference.
Increasingly, high density bar code and matrix dataforms are being utilized. Such dataforms provide for an increased amount of information encoded per unit area of the dataform as compared to non-high density dataforms. The minimum cell size of a dataform is defined as the smallest dimension of a separately readable information conveying portion of the dataform. High density dataforms may be advantageously be used with, for example, small electrical components where surface area of a component on which a dataform could be imprinted or affixed on a label is extremely limited. In such applications, minimum cell size of a high density dataform may be in the range of 2-4 mils. Two mils is 0.002 inch (0.05 mm.), while four mils is 0.004 inch (0.10 mm.).
Current art imaging-based dataform readers do not have optic assemblies capable of focusing a sufficiently sharp image of a target high density dataform onto a photosensor array to provide for efficient reading the high density dataform image. In addition, proper positional and angular alignment between the optic assembly and a center point of the photosensor array is critical. Lenses of the optic assembly must be precisely aligned longitudinally with the center point of the photosensor array and perpendicularly oriented thereto to obtain the sharpest possible image of a target high density dataform at the center point of the photosensor array. Even slight image distortion can prove detrimental in processing and decoding high density dataforms. Current art imaging-based readers do not have lens alignment structure capable of precise positional and angular alignment between the lenses of the optic assembly and a center point of the photosensor array. What is needed is an imaging assembly including a modular camera assembly having a optic assembly capable of focusing a sharp image of a target high density dataform onto a two dimensional photosensor array. What is also need is a modular housing and a optic assembly lens support structure or shroud supported within the housing that is capable of being accurately positioned with respect to the photosensor array to direct a sharp image of the target high density dataform onto a center point of the photosensor array such that the image of the target dataform can be decoded.